Oscillating air dispensers for microwave oven

ABSTRACT

Apparatus for transferring heat between temperature controlled air dispensed from a pair of oscillating ducts and a food product in a cabinet having an interior compartment bounded by front, side and rear walls. A foraminous partition, having a central portion and extremities, is mounted to divide the interior of the cabinet into a cooking chamber and an air conditioning chamber. It is configured to encircle a portion of the cooking chamber such that the air conditioning chamber extends around a major part of the periphery of the cooking chamber wherein air is drawn along multiple paths toward side walls and toward the rear wall from the cooking chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.07/723,250, filed Jun. 28, 1991, entitled "FOOD HANDLING SYSTEM" and acontinuation-in-part of application Ser. No. 07/463,279 filed Jan. 10,1990, now U.S. Pat. No. 5,147,994, entitled "MICROWAVE VENDING MACHINE."

TECHNICAL FIELD

The invention relates to improvements in recirculating air convectionovens for heating food products.

BACKGROUND OF INVENTION

In heavy duty foodservice ovens and food vending machines, cleaning is amajor consideration. This is particularly important in air recirculatingimpingement ovens of the type disclosed in U.S. Pat. No. 3,884,213 andin convection ovens with microwave food heating.

U.S. Pat. No. 3,884,213 discloses an oven equipped with a pivotallymounted, rectangular shaped, microwave transparent plate having spacedtubes extending therethrough for forming collimated jets of air that areprojected to impinge upon surfaces of a food product. While thedisclosed oven provided significant improvements in the transfer of heatto the food product, it was difficult to clean and maintain. Further,the shape and mounting for the jet plate did not permit optimum air flowto provide maximum efficiency and required that the jet plate bemicrowave transparent.

Vending machines for dispensing hot and cold drinks, candy, cookies,potato chips and other snack foods have enjoyed significant commercialsuccess. However, vending machines for dispensing meals have beenlimited to dispensers of refrigerated foods such as sandwiches, saladsand the like.

Devices heretofore devised for incorporating electronic ovens in foodvending machines are disclosed in U.S. Pat. No. 3,333,666; U.S. Pat. No.3,343,479; U.S. Pat. No. 3,386,550; U.S. Pat. No. 3,397,817; U.S. Pat.No. 3,534,676; U.S. Pat. No. 4,004,712; U.S. Pat. No. 4,398,651; U.S.Pat. No. 4,592,485; U.S. Pat. No. 4,762,250; U.S. Pat. No. 4,783,582 andU.S. Pat. No. 4,784,292.

Vending machines for hot meals generally include a refrigeratedcompartment for preserving food, a microwave oven compartment for fastcooking, and a conveyor for transferring food from the refrigeratedcompartment into the microwave oven. However, since vending machines forhot foods have enjoyed very limited commercial success, separatemicrowave ovens for heating food items removed from a refrigerator arecommonly employed in convenience stores, airports, cafeterias and otherfood vending operations.

Microwave heating of certain foods, including pizza and sandwiches thatcontain dough and bakery products, typically leaves the surface toomoist and less palatable than similar food products cooked in othertypes of ovens.

Ovens of the type disclosed in U.S. Pat. No. 3,884,213; U.S. Pat. No.4,154,861; U.S. Pat. No. 4,289,792; U.S. Pat. No. 4,409,453 and U.S.Pat. No. 4,835,351 employ air jets which impinge upon the surface of afood product to provide surface heating of the product in combinationwith microwave heating. Jet impingement ovens have enjoyed significantsuccess in commercial food service and commercial food processingoperations. However, a long felt need exists for apparatus for quicklyand efficiently heating food products that require little or nopreparation for use in a vending machine for hot meals and in countertop ovens for foodservice operations that are easily cleaned.

SUMMARY OF INVENTION

A preferred embodiment of the apparatus to transfer heat between streamsof recirculating air and a food product includes an oven cabinet havingan interior divided by a foraminous plate to prevent transfer ofmicrowave energy from a cooking chamber to an air conditioning chamberin the cabinet. The air conditioning chamber houses air circulatingapparatus to recirculate temperature controlled air from the airconditioning chamber through the cooking chamber to facilitate crispingand browning to provide a desired surface texture. The foraminouspartition has extremities spaced from and extending along sides of theoven such that recirculating air is drawn along multiple paths to theair circulating apparatus.

Microwave heating apparatus communicates with the cooking chamber toprovide rapid heating of the food by electro-magnetic excitation. Airdispensing ducts are mounted by a coupling which permits oscillation ofthe ducts about an axis to diffuse microwaves in the cooking chamber andto sweep collimated air streams across the surface of the food product.

In one embodiment of the invention, a method for controlling thetemperature and surface texture of a product includes the steps of:positioning a product in a container having upwardly extending sides anda bottom; positioning the product and container in a temperaturecontrolled atmosphere; supporting the product above the bottom of thecontainer; and forming a region of controlled air pressure alternatelyadjacent opposite sides of the product by directing air to flowalternately adjacent opposite sides of the product such that temperaturecontrolled air flows between the lower surface of the product and thebottom of the container.

DESCRIPTION OF DRAWINGS

Drawings of a preferred embodiment of the microwave vending machine areannexed hereto so that the invention may be better and more fullyunderstood, in which:

FIG. 1 is a perspective view of a package handling apparatus and ovencabinet inside a vending machine, the outer cabinet of the vendingmachine being broken away to more clearly illustrate details ofconstruction;

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2;

FIG. 4 is an exploded perspective view of the air dispensing apparatus;

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 1;

FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 1;

FIG. 7 is an exploded perspective view of a container and protectivesleeve that form a package for a food product;

FIG. 8 is an elevational view of the package illustrated in FIG. 7,parts being broken away to more clearly illustrated details ofconstruction;

FIG. 9 is a fragmentary diagrammatic view illustrating a modified formof a food container having susceptor film mounted therein;

FIG. 10 is a fragmentary diagrammatic view of a food container having abottom layer of french fried food material and an upper layer of adifferent food product;

FIG. 11 is a diagrammatic view illustrating air flow during a firststage of the cooking process; and

FIG. 12 is a diagrammatic view similar to FIG. 11 illustrating air flowduring a second stage of the cooking process;

FIG. 13 is a perspective view of the external vending machine cabinet;

FIG. 14 is a cross sectional view taken through the electro-mechanicallinear actuator;

FIG. 15 is a diagrammatic view similar to FIG. 11 illustrating air flowthrough a particulate food product;

FIG. 16 is a perspective view of a container having a lattice bridgingthe open top thereof;

FIG. 17 is a perspective view of the bottom of the container illustratedin FIG. 16;

FIG. 18 is a cross-sectional view taken along line 18--18 of FIG. 16;

FIGS. 19-21 are cross-sectional views similar to FIG. 18diagrammatically illustrating the progressive heating of a film sealingthe container to uncover a food product in the container;

FIG. 22 is a top plan view of a second embodiment of the oven, partsbeing broken away to more clearly illustrate details of construction;

FIG. 23 is a cross-sectional view taken along line 23--23 of FIG. 22;

FIG. 24 is a cross-sectional view taken along line 24--24 of FIG. 22;

FIG. 25 is a cross-sectional view taken along line 25--25 of FIG. 22;

FIG. 26 is a fragmentary perspective view of a pair of oscillating-airdispensing ducts;

FIG. 27 is a fragmentary elevational view of a portion of the partitionbetween the cooking chamber and the air conditioning chamber;

FIG. 28 is a cross-sectional view taken along line 28--28 of FIG. 27;

FIG. 29 is a cross-sectional view taken along line 29--29 of FIG. 27;and

FIG. 30 is an enlarged cross-sectional view through an oscillating airdispenser.

Numeral references are employed to designate like parts throughout thevarious figures of the drawing.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIGS. 1, 4, 7 and 13 of the drawings, the numeral 10generally designates a package that is moved by package handlingapparatus 40 into and out of an oven 70 in a vending machine 200. Aswill be hereinafter more fully explained, a source 90 of electromagneticradiation and air circulating apparatus 100 are employed for heating afood product 30 selected by a consumer upon depositing the purchaseprice of the food product in the vending machine 200 illustrated in FIG.13. As best illustrated in FIG. 13 of the drawing, the vending machine200 is preferably adapted to serve, for example, hot food products 30 toa customer within about one and a half to two minutes. In theillustrated embodiments, the food products 30 may, for example, includefrench fried potatoes, chicken nuggets, pizza, submarine sandwiches,bread and other baking products.

The vending machine 200 is mounted in an enclosure cabinet having a backwall 201, spaced side walls 202 and 204, a front panel 205, a top wall206 and a bottom wall 208. The front panel 205 is preferably hingedlysecured to side wall 202 and provided with a key actuated lock 210securing the front panel 205 in a closed and locked position to preventunauthorized access to the interior of the enclosure. A currencyreceiving mechanism 212 adapted to accept both coins and bills ismounted on front panel 205 along with a coin return slot 214 forreturning change to the customer.

Selector plates 216, 218, 220 and 222 are mounted on the front panel 205for use by the customer to designate the food item selected to be heatedand dispensed through a delivery passage 224 closed by a protective door225. Product identification panels 215, 217, 219 and 221 are associatedwith selector plates 216, 218, 220 and 222, respectively, to inform thecustomer what food item can be selected by touching one of the selectorplates. Identification panel 215 is provided with a graphic illustrationof fried potatoes permitting use of the vending machine 200 by personswho do not speak or read a particular language. Additional indiciaincluding words, numerals or other and graphic representations may beapplied to each of the panels 215, 217, 219 and 221.

A condiment holding chamber 209 is provided for holding packets of salt,pepper, sugar, ketchup, mustard and barbecue sauce.

As will be hereinafter more fully explained, a refrigerated food storagecabinet 170 is preferably mounted in the lower portion of the interiorof the vending machine enclosure 200 and package handling apparatus 40and oven 70 are mounted above and adapted to receive selected packagesof food products from the refrigerated storage compartment 170transported by an elevator 180.

Each selector plate 216, 218, 220 and 222 is preferably connected to anelectrical circuit adapted to initiate a sequence of events providedthat payment for the food item 30 has been received in the currencyreceiving mechanism 212. As will be hereinafter more fully explained,touching selector plate 220 indicates that pizza, graphicallyillustrated on product identification panel 219 is to be dispensed. Acontainer 10 containing pizza will be automatically moved from therefrigerated storage compartment 170 onto an elevator 180 and deliveredto the package handling apparatus 40 which will move the package 10 tooven 70 for heating and then dispense the heated product 30 through thedelivery passage 224 which is accessible to the customer by raising door225.

The electrical circuit controlling the heating of the selected foodproduct 30 preferably includes three programmed elements for deliveringa predetermined type of heating for a pre-programmed time interval tothe selected food product. The programmable circuit preferably includes,for example, devices to program the heating cycle by coordination withthe location of the selected food item in the storage compartment 170, abar code or other readable mechanism on the package, and symbolsdisplayed on or adjacent selector plates 216-222 for the user to touch.From the foregoing, it should be readily apparent that touching one ofthe selector plates 216, 218, 220 or 222 based on the visual selectionof a food item graphically illustrated on product identification panels215, 217, 219 or 221 initiates a programmed sequence to control theheating cycle of the selected food product 30.

Package 10, best illustrated in FIGS. 7 and 8, comprises a tubularsleeve 12 having open ends 13a and 13b. Sleeve 12 is formed by a top 14,bottom 15 and side walls 16a and 16b having peripheral edges connectedto form an interior cavity 17 for a container 18. Bottom 15 is narrowerthan top 14 and side walls 16a and 16b are inclined relative to verticalplanes.

Container 18 is an open topped tray formed by side walls 20 and 21having end walls 22 and 23 secured between opposite ends thereof and abottom wall 24. Support ribs 25 or other suitable projections extendupwardly from bottom wall 24 for supporting a food product 30 spacedfrom bottom wall 24 to provide space forming a path 28 extending betweenthe lower surface 31 of the food product 30 and the upper surface 25a ofthe bottom wall 24 of container 18.

The package 10 carries the food product 30 in the open-top container 18which is enclosed in the tube-like sleeve 12. The food product 30 isstored in a cabinet 170 in the container 18 inside of the sleeve covers12. The container 18 is withdrawn from the sleeve 12 prior to heatingthe food product 30 and then the food 30 and container 18 are returnedto the sleeve 12 to retain heat in the food until the package 10 isopened by the customer.

It should be readily apparent that refrigeration of food product 30 maynot be necessary if food product 30 is not perishable or if package 10containing the food product has been treated to assure that food product30 has sufficient shelf life. Cabinet 170 may be refrigerated or dividedinto compartments, some of which are refrigerated depending upon thenature of the food product to be dispensed by the vending machine 200.

The relatively non-conducting sleeve 12 serves as a comfortable holderfor the hot container 18 and food 30.

The cover for the container 18, having a lip 19 which extends around theperiphery of upper edges of walls 20, 21, 22 and 23, is formed by thetop 14 of sleeve 12 to provide a slip-over lid which covers the open topof the container 18 and can be removed for heating and subsequentlyprovides insulated cool handling of the hot product 30 by enclosing thelip 19 of the container 18.

In FIG. 9 of the drawing, the numeral 18a generally designates amodified form of the container having a susceptor belt 27 mountedadjacent bottom 24 of the container having ribs 25 formed thereon. Thesusceptor belt is formed of polyethylene terephthalate and iscommercially available from a variety of sources including Frigigold ofEngland and is recommended for use in reusable plastic or paperboardmicrowave cook ware in a recommended temperature range of up to 450° F.The susceptor belt 27 is rapidly heated by microwave energy until itreaches a maximum temperature of, for example, 350° F. and thetemperature level is maintained to provide radiant and conductive bottomheat to the food product 30.

In the embodiment of the container 18 illustrated in FIG. 10 of thedrawing, a layer 29 of a particulate food product, such as strips ofpasta or slices of potato, is positioned between the bottom wall 24 ofcontainer 18 and the lower surface 31 of food product 30. If layer 29 isslices of potato and product 30 is a meat product, juices dripping fromthe lower surface of food product 30 will contact and be absorbed bylayer 29 of potato slices to enhance the cooking of both the slices ofpotato and the meat product 30. The liquid juices enhance the flavor andappearance of the potatoes while the circulation of air through passages28 between the potato slices results in controlled drying andevaporation of moisture from the bottom of the food product 30 toprovide an acceptable texture, taste, smell and appearance superior tothat conventionally achieved in microwave ovens.

As illustrated in FIGS. 15-21 of the drawing, the food product 30a maycomprise particulate material, such as slices of fried potatoes and acorrugated susceptor belt 27 is mounted adjacent bottom 24 to form ribs25. Since the susceptor belt 27 is controllably heated by the microwaveand portions of the upwardly extending ribs 25 contact the lower surfaceof the food product, the structure simulates grilling as well asallowing juices to flow into the area between the ribs.

Container 18b, illustrated in FIG. 15, is provided with a sheet 27a of aheat shrinkable film bonded to lip 19 for sealing the food product 30ain the container 18b. A sheet 27a preferably formed of polymericcompounds and materials, for example, synthetic thermoplastic resins ofthe type which are commercially available from E. I. DuPont de Nemoursand Co. of Wilmington, Del., used to form a polyethylene film which willshrink when contacted by air at a temperature of less than 400° F. whichresults in film 27a becoming perforated and shrinking toward lip 19which extends around the periphery of container 18b. The cohesive natureof the polyethylene material prevents it from dripping into the foodcontainer. It should be readily apparent that the use of thepolyethylene film 27a provides a seal which prevents deterioration offood product 30a over an extended period of time in a refrigerator orfreezer.

A perforated grid or lattice 27b, illustrated in FIG. 16 and FIGS.18-21, may be mounted between the upper surface of lip 19 and the lowersurface of sheet 27a. Legs 27c and 27d spanning across the top ofcontainer 18b support film 27a to assure that portions of film 27a donot drop downwardly to engage the food product 30a in container 18b.

As diagrammatically illustrated in FIGS. 18-21 of the drawing, film 27aand lattice 27b are bonded or otherwise sealingly secured to the lip 19which extends around the periphery of the open top of container 18b toprevent dehydration and to otherwise protect food product 30a incontainer 18b. Food product 30 is supported on susceptor belt 27 havingupwardly extending projections 25 formed thereon for spacing the lowersurface of food product 30 above the bottom of container 18b to form airpassages therebetween as hereinbefore described.

As illustrated in FIG. 19 of the drawing, impingement of air stream 128aagainst the upper surface of film 27a causes a central portion of film27a to be perforated forming an opening 27a' in a central portion of thefilm intermediate edges of container 18b.

As illustrated in FIG. 20, opening 27a' is enlarged as heat istransferred to the film 27a which tends to roll back as indicated at27a" as the film material shrinks and is distorted.

As illustrated in FIG. 21 of the drawing, heat transferred to the film27a causes the meltable and shrinkable film 27a to retract to theposition designated 27a'" thereby uncovering the upper surface of foodproduct 30 in container 18b.

It should be appreciated that container 18b is preferably stored in atubular sleeve 12 of the type hereinbefore described to preventperforation of sealing film 27a during handling of containers whilebeing transported for stocking storage cabinet 170. As will behereinafter more fully explained, after container 18b has been movedinto heat exchange relation with streams 128a of heated air projected byair circulating apparatus 100, container 18b is reinserted into thetubular sleeve 12 prior to dispensing the food product to the customerso that the hot container 18b and the food product 30 therein can behandled by the customer to eliminate the necessity for providing "hotpads" or other apparatus for handling the hot container.

As best illustrated in FIGS. 1 and 14, package handling apparatus 40includes a container loading device 50 and a container unloading device60. The loading device 50 and unloading device 60 are of substantiallyidentical construction and comprise motors 51a and 51b, respectively,drivingly connected through synchronous drive belts 52 to the end ofdrive screws 56. Each drive screw 56 has threads formed on the outersurface thereof which engage internal threads in a drive nut 55 whichmoves linearly along drive screw 56 as the drive screw rotates. Thrustis transmitted from the drive nut 55 to a translating tube 57. Theentire screw 56 and nut 55 assembly is protected from contamination andenvironmental elements by a cover tube 58, and an end wiper seal 59.Rotational thrust bearings 54 allow the screw 56 to freely rotate underloaded conditions.

The electro-mechanical linear actuators 50 and 60 are commerciallyavailable from Jasta, Inc. of San Jose, Calif. and from Dayton ElectricManufacturing Co. of Chicago, Ill., and form no part of the inventionexcept in the claimed combination.

Motors 51a and 51b are preferably variable speed reversible synchronousgear motors. It should be readily apparent that motors 51a and 51btransmit torque through belt 52 for rotating drive screws 56. Rotationof drive screw 56 causes drive nut 55 which is secured to the inner endof translating tube 57 to move translating tube 57 to extend or retracttube 57 relative to cover tube 58.

As diagrammatically illustrated in FIG. 5 of the drawing,electro-mechanical actuator 60 having rake plate 57b mounted thereon ispivotally mounted between a pair of lugs 60a and is rocked in a verticalplane by a solenoid 60b connected to an actuating arm 60c secured tocover tube 58 of actuator 60.

When rake plate 57b is in its retracted home position indicated indashed outline at 57b in FIG. 5 of the drawing, rake plate 57b ispreferably positioned at an elevation above container 18 such that whentranslating tube 57 is extended to the full outline position, the loweredge of rake plate 57b moves above the upper edge of container 18. Whenrake plate 57b reaches the full outline position illustrated in FIG. 5of the drawing, solenoid 60b is actuated for moving rake plate 57bdownwardly to an elevation below the lip extending around container 18such that when translating tube 57 is retracted to the dashed outlineposition, container 18 will be returned through passage 48 in productguide member 46 and returned to the interior of tubular sleeve 12. Aftercontainer 18 has been deposited in tubular sleeve 12, solenoid 60b willagain be actuated for elevating rake plate 57b to a position above theupper edge of opening 48 such that pusher plate 57a may be actuated formoving the next container 18 into the oven.

Conveyor 65 includes a flexible belt 66 extending around a drive roller66a and a driven roller 66b, drive roller 66a being driven by areversible variable speed motor 68.

The in-feed conveyor, generally designated by the numeral 42, comprisesa paddle 43 suspended between chains 43a and 43b which extend arounddrive sprockets mounted on a shaft driven by a motor 43d. The in-feedconveyor 42 is mounted between guide members 44 and 46. As illustratedin FIG. 5, guide member 44 comprises a generally L-shaped member formedby substantially perpendicularly disposed legs 44a and 44b connected bya transition section 44c. Product guide member 44 is connected to asecond product guide member 46 by a front bracket 42f and a rear bracket42r. As illustrated in FIG. 1 of the drawing, an in-feed drive motor 43dis secured to guide member 46 and paddle 43 is moved between guidemembers 44 and 46 by chains 43a and 43b.

Product guide member 46, best illustrated in FIG. 5, is formed bygenerally perpendicularly disposed legs 46a and 46b connected by atransition section 46c. A third leg 46d extends generally parallel toleg 46b and has an end secured to an end of leg 46b by stop member 45.As will be hereinafter more fully explained, stop member 45 functions asa stop to limit movement of package 10.

Leg 46b of product guide member 46 has a first passage 47 formed thereinwhile section 44d has a second passage 48 formed therein. As will behereinafter more fully explained, when conveyor 65 moves package 10 intoengagement with backstop 45, the open end 13a of tubular sleeve 12 ispositioned adjacent opening 47 while the open end 13b of sleeve 12 ispositioned adjacent passage 48. When motor 51a of the linear actuator ofloader assembly 50 is energized, tube 57 and push plate 57a on the endthereof will move through passage 47 and through the open end 13b ofsleeve 12 for moving container 18 through the open end 13a of sleeve 12and through passage 48 into a cooking chamber in oven 70. Aftercontainer 18 is positioned in the cooking chamber, motor 51a isreversed, thereby retracting translating tube 57 and push plate 57a tothe position illustrated in FIG. 1 of the drawing.

After the product 30 in container 18 has been heated, motor 51b of thelinear actuator of the unloading assembly 60 will be energized to extendthe translating tube 57 of the unloading assembly 60 causing the rakeplate 57b to move into the cooking compartment above container 18 andthen pivot downwardly for engaging lip 19 on end wall 23 on container18. Motor 51b is then reversed for retracting tube 57 and rake plate 57bfor urging container 18 out of the oven 70, through passage 48 andthrough the open end 13a of sleeve 12. When motor 68 is energized, theheated food product 30 in container 18 which has been repositioned insleeve 12 will be moved toward the delivery end of conveyor 65.

Product guide members 44 and 46 are bolted or otherwise secured to theupper surface of loader base member 42a upon which in-feed conveyor 42and delivery conveyor 65 are mounted.

The oven 70 comprises spaced side walls 72 and 74, a back wall 76 and afront wall 78. Front wall 78 has an access opening 79 formed thereinwhich is opened or closed by a door 80. A microwave trap 81 is formedaround door 80 and is configured to prevent passage of microwave energythrough space between the periphery of the door 80 and walls of thecabinet 70. Top wall 71 and bottom wall 73 close upper and lower ends ofoven 70. Each wall of the oven is preferably formed by spaced metallicsheets and the space between the sheets is filled with thermalinsulation material.

An actuator 82, secured to mounting bracket 82a, is connected through alink 84 to door 80 for moving door 80 vertically relative to accessopening 79. Actuator 82 is preferably an electro-mechanical actuator ofthe type illustrated in FIG. 14 and is driven by a motor 51a.

Referring to FIGS. 1 and 2 of the drawing, the electromagnetic radiationdevice generally designated by the numeral 90 in the illustratedembodiment comprise a pair of magnetrons 92 connected to wave guides 93formed in side walls 72 and 74 of oven 70. The magnetrons 92 supplyelectromagnetic energy to wave guides which carry the energy to thecooking chamber. A preferred microwave frequency is 2450 megahertz.Magnetrons 92 are conventional vacuum tubes in the microwave oven thatconvert electrical energy to electro magnetic energy in the microwavefrequency spectrum. Waves of microwave energy are similar to radio wavesexcept they are higher frequency than radio waves and lower frequencythan ordinary light waves. The microwave energy is channeled throughwave guides 93 from the magnetrons 92 into the cooking chamber 120.

As illustrated in FIG. 2 of the drawing, the side walls 72 and 74 areformed by spaced sheets 74a and 74b and insulation material 74c isconfigured to form a guide tube 93 having a lower end 94 which isinclined at an angle 95 relative to a vertical plane 96 at an angle in arange between 15° and 75°. In the illustrated embodiment, the angle 95is approximately 45°.

The application of microwave radiant heating is delivered from two sidesand angles downwardly toward food 30 in an open top container 18. Sincethe container and the food in the-container do not reflect microwavessignificantly and since the space under the container diffuses microwavewhich passes through or by the container the beam from one wave guide isnot reflected directly into the other but is largely retained in theheating chamber.

Since the container 18 is non-metallic, reflections from one wave guide93 are not reflected into the other to keep microwave in the chamber 120to effectively heat the food 30.

The support, for the open package is preferably less than 25% reflectiveof the microwave.

The reflective surface of the bottom 24 of the container 18 is greaterthan one-fourth wave length, for 2450 megahertz (MHZ) microwaveone-fourth of 13 cm, below the surface of food being heating. The angleand the distance reduce standing waves in the small heating cavity.

A tube 103 is connected through a valve 103a to a supply of water orsteam and which may be used for delivering an atomized spray of water orsteam into the air conditioning chamber 115 for controlling the relativehumidity and dew point of air circulated through air conditioningchamber 115 and cooking chamber 120.

Referring to FIGS. 2, 3 and 4 of the drawing, air circulating apparatusgenerally designated by the numeral 100 comprises a blower housing 102having an inlet opening 104 and a discharge opening 106. As illustratedin FIGS. 2 and 4, blower housing 102 is in the form of a volute and aplenum section 108 is formed adjacent the discharge opening 106.

A radial flow fan impeller 110 draws air axially through inlet opening104 and discharges air radially through plenum section 108 and dischargeopening 106.

A heating element 112 having coils 113 of a first stage and coils 114 ofa second stage is mounted for heating air drawn into the blower housing102.

As best illustrated in FIG. 3 of the drawing, the interior of the ovencabinet 70 is divided by a perforated plate 75 to form an airconditioning chamber 115 and a cooking chamber 120. Perforated plate 75is constructed of a metallic material and has perforations 76a withrelatively small openings preferably equivalent to more than 50% of thesurface area. The perforated metal plate 75 prevents microwave energyfrom passing into the air conditioning chamber 115.

The perforated plate 75 forms a splatter shield on which airborne spoilaccumulates. Referring to FIGS. 27, 28 and 29 of the drawing, perforatedplate 75 is preferably a single sheet of metallic material having rowsof slits 77 which extend longitudinally of the sheet. Central portionsof the sheet are deflected along lines 77a, 77b, 77c and 77d, withoutremoving material from the sheet to form air passages through the sheet.Between adjacent slits 77 sections of the central portions of the sheetare deflected upwardly to form upwardly extending ridges 75a, by bendingthe material along lines 77a, 77b, 77c and 77d. Other segments of thesheet are deflected to form downwardly extending ribs 75b by bending thematerial downwardly along fold lines 77a-77d.

When adjacent segments 75a and 75b of sheet 75 are deflected in oppositedirections air passages 75c are formed in the sheet.

The perforated partition 75 constructed of metallic material and due toits geometric configuration forms a barrier which prevents passage ofmicrowave energy into the air conditioning chamber 115. Thissignificantly contributes to reducing the propagation of microwaveenergy through passages formed in the wall of the air conditioningcompartment through which fan drive shafts, electrical conductors, steaminjectors, and ventilation ducts are mounted.

Further, the perforated sheet 75 significantly aids in removing greaseand other particulate material from the recirculating air and ispreferably mounted for easy removal for cleaning.

In heavy duty food service ovens, cleaning is a major consideration.

Sheets of the same perforated material are preferably mounted to formremoval splatter shields 75s adjacent opposite sides of the food productto form an oven liner which is easily removable for cleaning. Soilcollector pans or trays 165 extend around the food product to catch anyfood particles which may be dislodged from the cooking container duringthe cooking process.

A coating or layer 75d of non-conductive insulator material is appliedto at least one surface of the perforated sheet 75. If it is deemedexpedient to do so, only top surfaces of deflected portions 75a betweenfold lines 77b and 77d may be coated with insulator material to preventmicrowave arcing between surfaces of perforated sheet 75 and a metallicpan surface.

Microwave energy at a frequency of 2,450 megahertz tends to arc when twometal surfaces approach each other at a low angle. The arcing not onlywastes heating energy, it can cause fires in dry products and can pitthe metal surfaces.

Heretofore, applying porcelain coatings to flat metallic sheets toprevent arcing has resulted in the porcelain coating tending to chip andcrack when the flat sheet of metal is deflected. However, the perforatedsheet 75 having portions 75a and 75b deflected outwardly in oppositedirections from a central planar portion 75p is relatively stiff whichsignificantly reduces the tendency of the ceramic coating 75d to crackor chip.

As best illustrated in FIG. 3 of the drawing, the first stage of coils113 is mounted in air conditioning chamber 115 outside of the blowerhousing 102 while the second stage of coils 114 is mounted inside blowerhousing 102. Terminals 112a and 112b of heating element 112 areconnectable to a suitable source of electricity.

As illustrated in FIG. 4 of the drawing, a mounting plate 116 having anotch 117 formed in the periphery thereof and a central opening 118 isbolted or otherwise secured to blower housing 102 for supporting heatingelement 112. Plate 116 is formed in two parts which are connectablealong a part line 119.

As illustrated in FIG. 3, blower 110 is mounted on a shaft which isdriven through a coupling 111 by a motor 110a.

Coils of a third stage heating element 109 are mounted in the plenumsection 108 of blower housing 102 and positioned such that air deliveredradially from blower 110 is heated immediately prior to being deliveredthrough discharge opening 106. It should be readily apparent that onlycoils 109 may be activated while coils 113 and 114 are idle, if it isdeemed expedient to do so depending upon the heating requirements of aparticular food product.

An air dispensing duct generally designated by the numeral 125 issecured to plenum 108 for receiving air from discharge opening 106.

As best illustrated in FIGS. 3 and 4 of the drawing, air dispensingapparatus 125 comprises a tapered duct formed by a perforated plate 126having an array of passages formed therein which communicate with tubes128. A front wall 130 and a rear wall 132 extend upwardly from theperforated plate 126 and are connected between side walls 134 and 136.An inclined top wall 138 extends between front wall 130 and a flange 140encircling the lower end of plenum 108 and enclosing the dischargeopening 106 from the blower housing 102.

As illustrated in FIG. 3 of the drawing, air directing vanes 143 extendbetween side walls 134 and 136 of the tapered duct 125 for distributingair along the length of the interior 144a of the tapered duct 125. Airdirecting vanes 143 are configured to deliver temperature controlled airinto the duct substantially parallel to a longitudinal axis 125a ofduct. Streams 128a and 128b of air are directed transversally of theaxis 125a from said duct toward the food product 30. As the ductreciprocates about the axis 142a of pin 142, which is parallel to theaxis 125a of the duct, streams 128a and 128b of air impinge on discreteareas on the surface of the food product 30 to transfer heat between theair streams and the surface of the food product 30.

The air dispensing apparatus 125 is pivotally secured to duct plenum 108by a pivot pin 142 extending through aligned apertures 144 in flange140. Pivot pin 142 extends into an opening 145 formed in lug 146 onshaft 148 which extends into an aperture 149 on a link 150. Link 150 hasan elongated slot 152 formed therein into which a pin 154 on crank 155extends.

Crank arm 155 has an aperture which receives a drive shaft 158 driven bymotor 160 through a gear reducer 161.

A radial blower 110 discharges its highest velocity air from the outerportion of the volute downwardly through shaped openings in tubes 128 toimpinge upon a narrow food product 30 in the open top container 18.

The air dispensing duct 125 is moved relative to the product 30 to giveuniform coverage by the air streams. As best illustrated in FIGS. 11 and12, the end walls 22 and 23 of the container 18 cause a portion of theair stream to be deflected to heat the sides and bottom 31 of product 30in the container. The movement applies the air streams near one side ofthe container adjacent end wall 22 and then to the other side adjacentend wall 23 so that parts of the air streams are alternately applied toopposite exposed sides of the product 30 and are caused to alternate thelateral flow through loose stacks of food products 30 such as curled orrandom lengths of french fried potatoes. This alternating lateral airflow through paths 28 between support ribs 25 passes under and heats thelower side 31 of irregularly shaped products such as bone-in chickenparts.

The effectiveness of the sideways air heating of lower surfaces 31 canbe enhanced by ribs 25 to provide air passages under flat products.

Further, the moving air dispensing apparatus 125 provides movingreflective surfaces which serve as stirrers to help distribute themicrowave energy in the cooking chamber 120.

The combination of extended orifices through tubes 128, and the open topcontainer 18 provides air escape path 129 while bringing the orifice toan optimum distance from the product 30. It should be noted that upperedges of the sides 20 and 21 and ends 22 and 23 of container 18 extendabove the height of the contained product 30 to enhance air flow betweenthe lower surface 31 of the product 30 and the bottom 24 of container18.

As illustrated in FIG. 2 of the drawing, streams of air dispensed fromair dispensing duct 125 through hollow air dispensing tubes 128 impingeupon the upper surface of a food product 30 in container 18. The spentair travels through space 129 between tubes 128, as illustrated in FIGS.11 and 12 of the drawing. Spent air travels upwardly adjacent baffles75s and the recirculating air is drawn upwardly through passages 75cformed in the perforated plate 75.

Soil collector pans 165 are preferably removably mounted and aremaintained at a temperature which is less than the temperature of anyother surface in the oven 70 for causing very fine smoke-type particlesin the moving air to be collected on the coldest surface in therecirculating path. To assure that the soil collection pans 165 aremaintained cooler than other surfaces in oven 70, the pans may beexposed to outside air or water cooling to facilitate collecting aerosolfrom the recirculating air.

From the foregoing it should be readily apparent that the disclosedmethod for controlling the temperature and surface texture of a foodproduct which is to be delivered from vending machine 200 generallycomprises delivery of a suitably packaged and preserved food productfrom a storage compartment 170 to an oven 70. The package 10 ispositioned by back stop member 45 in a predetermined relationshiprelative to electro-mechanical linear actuators 50 and 60 and relativeto access opening 79 communicating with cooking chamber 120 in oven 70.

Actuation of the actuator of the loading device 50 results in movementof push plate 57a through tubular sleeve 12 for pushing container 18bout of sleeve 12 and into the cooking chamber 120. Streams 128a of airdelivered through tubes 128 of the air circulating apparatus 100 meltsand shrinks film 27a for uncovering food product 30 in the open topcontainer 18b.

In the embodiment illustrated in FIG. 15 of the drawing, one or more airstreams 128a, after causing the food product 30a in container 18 to beuncovered will be delivered through the open top of container 18b. Ifthe food product 30a in the container is strips or slices of pasta,potatoes or other particulate material, air from stream 128a will bedelivered through the stacked material in heat transfer relation withthe surface of the pieces of the food product.

If food product 30 is a solid article as designated by the numeral 30 inFIGS. 11 and 12 of the drawing, air dispensing duct 125 is preferablyrocked causing air streams 128a and 128b to move across the surface ofthe food product between lateral edges thereof such that regions ofcontrolled air pressure are alternately formed adjacent opposite sidesof the product 30 such that temperature controlled air flows throughpassage 28 between the lower surface 31 of the food product and theupper surface 25a of the bottom 24 of container 18.

After the surface of the food product 30 has been heated by air streams128a and 128b, the recirculating air tends to limit localized heating ofthe product by microwave energy delivered by magnetrons 92. Tips, andthin areas of the product which are rapidly heated by the microwaveenergy may actually dissipate heat to air in streams 128a and 128b toprovide cooling to certain portions of the food product.

After the food product 30 in container 18 has been sufficiently heated,air flow through the air circulating apparatus 100 is terminated,magnetrons 92 are turned off and blower actuator 82 is energized formoving the door upwardly to the position illustrated in FIG. 1 of thedrawing. The electro-mechanical actuator of the container unloadingdevice 60 is then actuated for moving rake plate 57b from the dashedoutline position in FIG. 5 of the drawing to the full outline position.Rake plate 57b is then lowered and retracted for moving container 18 outof the oven and redepositing the hot container and the food therein inthe tubular sleeve 12.

After the heated food product and container 18 have been moved into theprotective tubular sleeve 12, conveyor 65 is energized for moving theheated food product toward the delivery passage 224 of the vendingmachine 200 such that the product is accessible to the customer byopening protective door 225.

SECOND EMBODIMENT

A second embodiment of the oven is illustrated in FIGS. 22-30 of thedrawings.

The second embodiment of the oven, generally designated by the numeral270, in FIGS. 22-25 of the drawing, comprises spaced side walls 272 and274, a back wall 276 and a front wall 278. The front wall 278 has anaccess opening 279 formed therein which is opened and closed by a door280. A top wall 271 and a bottom wall 273 close upper and lower ends ofthe oven 270. A microwave trap 281 is formed around door 280 and isconfigured to prevent passage of microwave energy through space aroundthe door.

Magnetrons 292a and 292b are connected to wave guides 293a and 293bwhich extend horizontally across an upper portion of the oven. Microwaveenergy is delivered into an interior compartment in oven 270 throughopenings 296a and 296b.

As best illustrated in FIGS. 22 and 25, opening 296b is formed in topwall 271 adjacent the door 280 and is positioned substantially equaldistances between side walls 272 and 274. Opening 296a extends throughtop wall 271 rearwardly of opening 296b and wave guides 293a and 293bare positioned perpendicular to each other.

As best illustrated in FIGS. 22 and 25 of the drawing, wave guide 293aextends longitudinally of the oven, magnetron 292a being mountedadjacent the rear wall 276 of the oven. Electromagnetic energy isdelivered from magnetron 292a through wave guide 293a extendinglongitudinally of the centerline 270c of the oven 270 into the oventhrough an opening 296a.

The second magnetron 292b is mounted adjacent a side wall 274 of theoven and delivers microwave energy through a horizontally disposed waveguide 293b, extending perpendicular to the centerline 270c of the oven,and through outlet 296b into the cooking chamber 320.

Microwave energy traveling through a wave guide into a microwave cookingcavity tends to form hot spots which are 2.4 inches apart directly belowthe opening into the cooking chamber, the hot spots being aligned withthe length of the wave guide. Providing two wave guides 293a and 293bwhich extend perpendicular to each other results in the formation offour hot spots positioned adjacent four corners of a square.

Referring to FIGS. 22, 23 and 24 of the drawing, air circulatingapparatus generally designated by the numeral 300 comprises a blowerhousing 302 having upper and lower discharge openings 306a and 306bwhich extend horizontally above and below a radial flow fan impeller310. A heating element 312 is mounted adjacent the inlet 304 into thefan housing.

As best illustrated in FIG. 25, the interior of the cabinet 270 isdivided by a foraminous splatter shield 275 to form an air conditioningchamber 315 and a cooking chamber 320. The partition 275 is preferablythe same material as the partition 75 hereinbefore described in thedescription of the first embodiment and illustrated in FIGS. 27, 28 and29 of the drawing. In the illustrated embodiment of the invention, theair conditioning chamber 315 is spaced horizontally from the cookingchamber 320 so that the air conditioning chamber 315 is in the back ofthe oven and the cooking chamber 320 is in a front portion of the oven.

As best illustrated in FIG. 22, the foraminous partition 275 has acentral portion 275a and extremities 275b and 275c configured toencircle a portion of the cooking chamber 320 such that the airconditioning chamber 315 extends around a major part of the periphery ofthe cooking chamber 315. Air is drawn along multiple paths toward sidewalls 272 and 274 and toward rear wall 276 from cooking chamber 320.

An upper plenum 308a and a lower plenum 308b are formed by a plenum wall316 extending generally parallel to back wall 276. Plenum wall 316 has agenerally vertically extending central portion 316aand generallyhorizontally extending upper and lower portions 316b and 316c,respectively. The central portion 316a has an opening 304 in whichradial flow fan 310 is mounted.

A pair of circular tubular members 317 extend outwardly from spacedopenings in the upper portion of the plenum wall and telescopicallyextend into circular sleeves 340 formed on air dispensing ducts 325a and325b which oscillate about spaced axes 325x and 325y, as will behereinafter more fully explained.

Referring to FIGS. 26 and 30, each air dispensing duct 325a and 325bcomprises a body portion having a tapered cross section formed betweenspace side walls 334 and 336 having outward extending flanges formedthereon.

A sheet of perforated material 343 having large and small apertures 343aand 343b formed therein is supported inside of each tapered duct 325aand 325b. A jet plate 326 having a plurality of spaced apertures 328formed therein has inwardly projecting guide surfaces formed on upperends of side walls such that the jet plate 326 is suspended from theflange extending along lower edges of side walls of the tapered ducts.The jet plate 326 is slidable longitudinally of the tapered duct so thatit can be easily removed for cleaning.

The perforated plate 343 mounted inside the tapered duct has openings toform a slight back pressure in each tapered duct to maintain airpressure substantially uniform longitudinally of the duct. Thecombination of the tapered cross section of the duct and the perforatedplate 343 contribute to provide a uniform air flow through each of theorifices 328 formed in the jet plate 326.

Further, openings 343a and 343b in the perforated plate 343 areconfigured to prevent passage of microwave energy from the cookingcompartment 320 into the air dispensing ducts 325a and 325b.

As best illustrated in FIGS. 23 and 24 of the drawing, air dispensingducts 325a and 325b comprise tapered ducts similar to the duct 125described in connection with the first embodiment.

As best illustrated in FIG. 26 of the drawing, each air dispensing duct325 comprises a tapered duct formed by a perforated plate 326 having anarray of passages 328 formed therein. A front end wall 330 and a rearend wall 332 extend upwardly from the perforated plate 326 and areconnected between side walls 334 and 336. The inclined top wall 338extends between front wall 330 and a flange or sleeve 340 encirclingtubular member 317 which forms an outlet from plenum 308.

The air dispensing apparatus 325a and 325b is pivotally secured totubular member 317 by a pivot pin 342 extending through an aperture 344ain hanger 344.

A shaft 345 is welded or otherwise secured to cross members 345a an 345bwhich extend diametrically across tubular sleeve 340.

As best illustrated in FIG. 26 of the drawing, a disk 346 is mounted onthe outer end of each shaft 345 and a connector link 348 is pivotallysecured between disks 346 on shafts 345 of each air dispensing duct 325aand 325b.

One of the disks 346 is connected through a link 349 to a disk 355mounted on the end of a drive shaft 358 from a gear drive driven by amotor 360.

From the foregoing it should be readily apparent that motor 360 rotatesdisk 355 which imparts reciprocating motion through link 349 to disks346 mounted on shafts 345. As link 349 reciprocates the oscillatorymotion of one disk 346 is transferred to the second disk 346 such thatair dispensing ducts 325a and 325b reciprocate in unison relative to thefood product 30 to provide uniform coverage by the air streams.

A lower tapered duct 325c, best illustrated in FIG. 24, which issignificantly wider than the upper oscillating air dispensing ducts 325aand 325b delivers air streams upwardly to impinge against the bottom ofa pan or a product supported on a rack 327 in the bottom of the oven.

From the foregoing it should be readily apparent that the apparatushereinbefore described for transferring heat between temperaturecontrolled air and a food product has multiple air dispensers 325a and325b. Oscillation of multiple ducts 325a and 325b provides a moreuniform sweeping action of air streams which project into the cookingchamber than could be accomplished with a single jet plate havingapertures spaced across the entire length of the cooking chamber. Themultiple air dispensers remain a substantially uniform distance from afood product in the cooking chamber as the air streams are moved acrossthe surface of the food product.

The foraminous partition 275 having a configuration approximating thatof the cooking chamber forms foraminous walls 275a, 275b and 275c aroundthe food product for collecting any material which may splatter duringthe cooking process. Further, the foraminous walls 275a, 275b and 275cspaced from side walls 272 and 274 and rear wall 276 form a generallyU-shaped air conditioning chamber 315 around the cooking chamber 320.Spent air flowing from the cooking chamber is drawn through openings inthe foraminous side partition walls 275b and 275c and also through thecentral rear foraminous partition wall 275a. Thus, it should be readilyapparent that air dispensed into the cooking chamber through theoscillating upper air dispensing ducts will be drawn away from oppositesides of the row of openings 328 formed in each air dispensing duct 325aand 325b. This minimizes the possibility that spent air will be drawnalong a path which will wash out air streams dispensed from the airdispensing ducts.

Openings 328 in the upper air dispensing ducts 325a and 325b arepreferably larger in diameter than the openings 329 formed in the lowerair dispensing duct 325c.

It has been observed that air delivered through an orifice can beprojected a distance about eight times the diameter of the openingbefore it loses its integrity and significantly diffuses. In a preferredembodiment of the invention, openings in the upper air dispensers arepreferably, for example, about one inch in diameter and the uppersurface of the food product is in a range between about two inches andeight inches from the lower surfaces of the oscillating ducts 325a and325b.

Openings formed in the lower jet finger, in the illustrated embodiment,are configured to impinge against a lower pan surface constructed ofthermally conducted material. Thus, the lower tapered duct 325c isprovided with smaller openings 329 spaced closer together than thoseformed in the upper air dispensing ducts 325a and 325b. In a preferredembodiment, the lower tapered duct is provided with apertures having adiameter of for example one-half inch and are positioned in a rangebetween one and four inches of the bottom of the pan supporting the foodproduct.

In the illustrated embodiment, the pan containing the food product doesnot move relative to the lower air dispensing duct.

In certain applications, if heat is not conducted by the pan away fromspots upon which the lower jets impinge fast enough to providesubstantially uniform heating to the bottom of the food product, eitherthe lower jet finger or the product support may be moved relative to theother for sweeping air streams across the bottom surface of the pan.

It should be readily apparent that the foraminous partition 275a, plenumwall 316 and the perforated plate 343 inside each air dispensing duct325a and 325b creates zones of differential pressure throughout the ovencompartment for enhancing and controlling air flow therethrough. Theradial flow fan 310 draws air from the air conditioning chamber 315creating an area of low pressure and delivers air into the upper andlower plenums 308a and 308b creating areas of high air pressure. Theperforated plates 343 in the upper and lower air dispensing ducts 325aand 325b and in the lower air dispensing duct 325c create a slight backpressure in each air dispensing duct for maintaining substantiallyuniform air pressure longitudinally of each air dispensing duct eventhough openings 328 and 329 are formed in the air dispensing ducts.

Since the foraminous partition 275 extends around a substantial portionof the periphery of the cooking chamber 320, air is drawn along multiplepaths away from the food product 30 after the air streams impingeagainst the surface of the food product and diffuse. This allows thespent air to be expeditiously removed from the cooking chamber whileminimizing diffusion of the air streams before they impinge upon thesurface of the food product.

Further, the foraminous partition 275 is easily removable from thecooking chamber when door 280 is opened for cleaning or replacement witha clean foraminous partition.

The shape and configuration of the foraminous partition 275 facilitatescollection of splattered material and its position in the stream ofrecirculating air causes it to be maintained at a temperature which islower than the temperature of other surfaces in the cooking chamber. Itshould be readily apparent that spent air which impinges against thesurface of a cold food product 30 will be at a lower temperature when itpasses through the foraminous partition than air in the air stream whichhas been heated by the heating elements 312 in the air conditioningchamber 315 and delivered through the plenum to the air dispensing ducts325a and 325b. Airborne particles and smoke in the circulating air tendsto be collected on the coolest surfaces in the oven. This preventstransfer of airborne contaminants into the air conditioning chamber 315for accumulation on surfaces which are difficult to clean.

As noted above, passages in the foraminous partition 275 are configuredto prevent the transfer of microwave energy from the cooking compartment320 into the air conditioning compartment 315 which significantlyreduces the possibility of leakage of microwave energy through openingsin the air conditioning compartment through which fan motor driveshafts, electrical conductors and the like extend.

The positioning of oscillating air dispensers 325a and 325b closelyadjacent opposite sides of openings 296a and 296b through whichmicrowave energy is delivered into the cooking chamber stirs themicrowave as the air dispensing ducts oscillate. Moving surfaces of theoscillating ducts also change constantly to diffuse standing waves ofreflected microwave energy in the cooking compartment. Any hot spotsformed by the microwave energy in the cooking compartment are diffusedby the oscillating ducts as the air streams are swept through thecooking chamber to provide more uniform heating by both the microwaveenergy and the impinging air streams.

Since microwave energy is contained in the cooking compartment andisolated from the air conditioning compartment, fresh air may becirculated through the air conditioning compartment 315 if it is deemedexpedient to do so for removing smoke and eliminating rancid odors.

The transfer of heat between temperature controlled air and a foodproduct is enhanced by delivering temperature controlled air,substantially parallel to an axis 125a in the embodiment of FIG. 3 oraxis 325x in the embodiment of FIG. 24, into the air dispensing ductbecause air is uniformly distributed and air pressure is substantiallyconstant along the length of each duct. This improves the efficiency ofthe air flow for dispensing streams of air from the duct toward the foodproduct in a direction generally transverse of axis 325x and generallyperpendicular to the food surface.

Reciprocation of the duct about axis 325x sweeps the streams of air thatimpinge on discrete areas on the surface of the food product across thesurface of the food product.

We claim:
 1. A method for transferring heat between temperaturecontrolled air and a food product comprising:providing a volume oftemperature controlled air; delivering temperature controlled airsubstantially parallel to a longitudinal axis of an air dispensing meanwhich includes an elongated hollow duct having an interior andpositioning parallel to said longitudinal axis; dispensing a stream ofair from said duct toward the food product in a direction generallytransverse to said longitudinal axis; and reciprocating said duct abouta reciprocating axis that is parallel to said longitudinal axis wherebysaid stream of air impinges on discrete areas on the surface of the foodproduct as said duct reciprocates.
 2. A method of transferring heataccording to claim 1, the step of delivering temperature controlled airsubstantially parallel to an axis into a duct comprising the stepsof:delivering air through an array of air directing vanes fordistributing air along the interior of the elongated hollow duct.
 3. Amethod of transferring heat according to claim 1, the step of deliveringtemperature controlled air substantially parallel to a longitudinal axisinto a duct comprising the steps of:delivering air through a tubularmember; and mounting said duct for reciprocal movement about saidtubular member.
 4. A method for transferring heat between temperaturecontrolled air and a food product according to claim 1, the step ofdelivering temperature controlled air substantially parallel to saidaxis into a duct comprising the steps of:drawing spent air resultingfrom impingement of said stream on discrete areas on the surface of thefood product along an air return path; positioning a foraminous memberhaving passages formed therein whereby said spent air flows through saidpassages in said foraminous member, said foraminous member beingconfigured whereby airborne particles in said spent air are retained bysaid foraminous member.
 5. A method according to claim 4, saidforaminous member forming a removable splatter shield extending acrosssaid return path.
 6. Apparatus for transferring heat between temperaturecontrolled air and a food product comprising:a plenum having an airreturn opening; a substantially circular outlet on said plenum having acentral axis; an elongated duct having a substantially circular entranceopening and an outlet opening; means supporting said duct for reciprocalmovement about said central axis; and a substantially circular couplerhaving a longitudinal axis for placing said substantially circularentrance opening in said duct in fluid communication with saidsubstantially circular outlet on said plenum whereby air is deliveredsubstantially parallel to said longitudinal axis from said plenum intosaid duct, said central axis and said longitudinal axis aresubstantially being parallel.
 7. Apparatus for transferring heat betweentemperature controlled air and a food product according to claim 6, saidcoupler comprising:a sleeve configured to encircle a portion of saidsubstantially circular outlet.
 8. Apparatus for transferring heatbetween temperature controlled air and a food product according to claim6, said coupler comprising:means delivering air through said entranceopening in a direction substantially parallel to said axis about whichsaid duct reciprocates.
 9. Apparatus for transferring heat betweentemperature controlled air and a food product according to claim 8, saidoutlet opening in said duct being configured to dispense a stream of airto impinge against the surface of a food product.
 10. Apparatus fortransferring heat between temperature controlled air and a food productaccording to claim 6, with the addition of: an array of air directingvanes in said elongated duct for distributing air in said elongated ductbetween said substantially circular entrance opening and said outletopening.
 11. Apparatus for transferring heat between temperaturecontrolled air and a food product according to claim 6, said elongatedduct comprising: a body portion having a tapered cross-section formedbetween spaced side walls; and a plate extending between said spacedside walls, said outlet opening being formed in said plate. 12.Apparatus for transferring heat between temperature controlled air and afood product according to claim 11, said plate having a plurality ofspaced outlet openings; and a perforated plate in said elongated ductadjacent said plate to form a slight back pressure in said elongatedduct to maintain air pressure substantially uniform longitudinally ofsaid elongated duct.
 13. Apparatus for transferring heat betweentemperature controlled air and a food product according to claim 12,said perforated plate having an array of passages through which airflows to said outlet openings.
 14. Apparatus for transferring heatbetween temperature controlled air and a food product according to claim6, said means supporting said duct for reciprocal movement about saidaxis comprising: at least one cross member secured to said elongatedduct and extending across said entrance opening; and a shaft secured tosaid cross member.
 15. Apparatus for transferring heat betweentemperature controlled air and a food product according to claim 14,said means supporting said duct for reciprocal movement about said axisfurther comprising: a link mounted for reciprocal movement connected tosaid shaft whereby reciprocal movement of said link causes said shaftand said elongated duct to oscillate about said axis.
 16. Apparatus fortransferring heat between temperature controlled air and a food productcomprising:a cabinet having an interior compartment; front, side andrear walls on said cabinet extending around said compartment; a plenumwall in said compartment having an opening, said plenum wall forming aplenum in said compartment; partition means spaced from said plenum walldividing the interior of the cabinet into a cooking chamber and an airconditioning chamber; air circulating means drawing air from saidcooking chamber to pressurize said plenum; temperature control means insaid air conditioning chamber for controlling temperature of air in saidair conditioning chamber; air dispenser means having a longitudinalaxis; means mounting said air dispenser means such that pressurized airfrom said plenum is delivered substantially parallel to saidlongitudinal axis into said air dispenser means and whereby spacedstreams of air are dispensed transversely of said longitudinal axistoward a food product in said cooking chamber; and means forreciprocating said air dispenser means about a reciprocating axis thatis parallel to said longitudinal axis for causing said air streams tosweep over the surface of the food product.
 17. Apparatus fortransferring heat between temperature controlled air and a food productcomprising:a plenum having an air return opening; a foraminous memberhaving substantially planar portions and having deflected portionsforming passages permitting flow of air through said passages in adirection generally parallel to said planar portion of said foraminousmember whereby the direction of air flowing generally perpendicular tosaid foraminous member enroute to said air return opening in said plenumis changed from a first direction generally perpendicular to saidforaminous member to a second direction generally parallel to saidforaminous member and then to a third direction generally perpendicularto said foraminous member; an outlet on said plenum having a centralaxis; an elongated duct having an entrance opening and an outletopening; means supporting said duct for reciprocal movement about saidaxis; and coupler means having a longitudinal axis for placing saidentrance opening in said duct in fluid communication with said outletopening on said plenum whereby air is delivered substantially parallelto said longitudinal axis from said plenum into said duct.
 18. Apparatusfor transferring heat between temperature controlled air and a foodproduct according to claim 17, said foraminous member having anon-conductive coating to electrically insulate said foraminous member.19. Apparatus for transferring heat between temperature controlled airand a food product according to claim 17, said deflected portions ofsaid foraminous member being formed to provide passages on oppositesides of said deflected portions wherein streams of air flowing in afirst direction generally perpendicular to said foraminous member form aplurality of streams of air flowing generally parallel to saidforaminous member which collide to change direction to said thirddirection generally perpendicular to said foraminous member.